The communications industry is rapidly changing to adjust to emerging technologies and ever increasing customer demand. This customer demand for new applications and increased performance of existing applications is driving communications network and system providers to employ networks and systems having greater speed and capacity (e.g., greater bandwidth). In trying to achieve these goals, a common approach taken by many communications providers is to use packet switching technology.
Content-addressable memories (CAMs), including, but not limited to, binary content-addressable memories (binary CAMs) and ternary content-addressable memories (ternary CAMs or TCAMs) are often used in packet switching device in processing of packets. Each entry of a binary CAM typically includes a value for matching against, while each TCAM entry typically includes a value and a mask. The binary or ternary CAM compares a lookup word against all of the entries in parallel, and typically generates an indication of the highest priority entry that matches the lookup word. An entry matches the lookup word in a binary CAM if the lookup word and the entry value are identical, while an entry matches the lookup word in a TCAM if the lookup word and the entry value are identical in the bits that are not indicated by the mask as being irrelevant to the comparison operations.